Solution

39196

First name
Fiona and Mahdi
School
Edith Neville
Country
Age
9

First we remembered that there are 1000g in 1kg. Then, we converted the weights by 1000. So 7.35kg x 1000 = 7350g.
8.20kg x 1000 = 8200g.
6.45kg x 1000 = 6450g.
And then we wrote points on the end.
7350 points
8200 points
6450 points
The biggest watermelon was 8.20 = 8200g.